Two casing geometries have widely been accepted for electric low-voltage power fuses. As a general rule, fuse casings are formed by insulating tubing cylindrical at the inside and at the outside thereof and having uniform wall thickness. In some instances a substantially prismatic casing geometry is preferred. To be more specific, it is desired in such instances that the casing be bounded outwardly by four planar surfaces enclosing right angles and forming externally rounded edge regions of increased wall thickness. Such casings are closed by a pair of terminal plates affixed to them by a plurality, i.e. four fasteners. These fasteners have shanks which project through the terminal plates into the edge regions of increased wall thickness of the casing.
Either of the two aforementioned types of fuses has specific advantages and specific limitations. It is the principal object of this invention to provide fuses which combine advantages of the two aforementioned types of fuses and are not subject to the limitations of the last referred-to type.
One of the most serious limitations of the last referred-to type of fuses resides in the fact that it has not been possible, heretofore, to manufacture the casings thereof at non-prohibitive cost of materials other than ceramic materials, in particular synthetic-resin-glass-cloth laminates. It is, therefore, a specific object of this invention to overcome this limitation, i.e. to provide fuses of the last referred-to type having casings of a synthetic-resin-glass-cloth laminate.
Further objects and advantages of this invention will become apparent as this specification progresses.